It was only recently that Khloe Kardashian learned the name of the son she had with ex-boyfriend Tristan Thompson. She revealed it in the first episode of Hulu's "The Kardashians" Season 3, but her best friend Malika Haqq had leaked it on Instagram shortly before that. And while we thought Tatum Robert's last name was Thompson, new reports indicate that it was not initially so and that his last name was Kardashian.

According to Page Six, he is now Tatum Thompson (his sister True also has their father's last name), but was originally Kardashian. Sources say that Tatum, now 10 months old, was initially listed as "Baby" because Kardashian took the time to name her. Since there is no Jane or John Does in California, it was apparently listed as "Baby."

"The specific reason for the name swap has not been disclosed, but it is likely related to the fact that the former couple was expecting a boy through surrogacy when news broke that the NBA player had secretly conceived Maralee Nichols," the magazine reported.

Trouble between Thompson and Kardashian began in 2018, just before the birth of their daughter True in April of that year. It lasted until 2019, when Thompson was accused of meeting Kardashian's sister Kylie Jenner's then best friend Jordyn Woods. The couple reunited during the pandemic and chose to expand their family shortly before news of Thompson and Nichols' affair became public.

"Khloe has always wanted a little brother for True, and with the support of her family, she went ahead with the birth," a source told Page Six.

Thompson and Kardashian, while not romantically involved, are co-parenting and recently looked united at True's kindergarten graduation; the two attended their daughter's school ceremony and were photographed smiling together.

"According to witnesses, they were conversing amiably and seemed to be on good terms," Page Six reported.